Pneumatic motor for medical instruments

ABSTRACT

The invention relates to a small pneumatic motor for a rotating medical instrument, especially for drilling or milling instruments. A shaft with a turbine is supported in a housing with the gas inlet end of the turbine arranged towards the output end of the motor. The driving gas flows to the turbine inlet side via channels arranged longitudinally in the housing along the periphery of the turbine and then back to the input end of the housing. Discharge of driving gas at the output end of the housing toward the patient is avoided in this way.

United States Patent 1 1 Pohlet al. 1 Jan. 9 1973 [54] PNEUMATIC MOTORFOR MEDICAL 3,434,679. 3/1969 Kutney et al. ..417/408 I INSTRUMENTS3,584,629 6/1971 08f ..128/305 3,472,323 /1969 Hall ..4l5/503 entors:Fritz (9. Pohl; A nold Keller, both of 3,128,079 4/1964 DeGroff.....415/503 K e t Germany 751,261 2/1904 Clarke ..415/503 x [73] AssigneezHowmet International, Inc. zweit 3,423,068 1/1969 Hall ..4l5/503Xniederlassung Kiel, Kiel- Dietrichsdorf, Germany Primary ExammerAllan D.Herrmann Att0mey-Beaman & Beaman [22] Filed: Aug. 7, 1970 [21] Appl.No.: 62,020 57] ABSTRACT The invention relates to a small pneumaticmotor for a Foreign Application Priority Data rotating medicalinstrument, especially for drilling or milling instruments. A shaft witha turbine is sup- Oct. 28, 1969 Germany ..P 19 54 130.1 p e in a housingwith the g inlet end of the bine arran ed towards the out ut end of themotor. 52 U. g P 1 S Cl g gg ig -iii 9 55 The driving gas flows to theturbine inlet side via 5 Int CL m 1/05, f 1/10 A6,) 17/32 channelsarranged longitudinally in the housing along 58 Field 61 Search..415/503,182, 199; 192/3 R, the Periphery of the turbine and hack the92 3 3 32/26 128/305; input end of the housing. Discharge of driving gasat 417 403 the output end of the housing toward the patient is avoidedin this way. [56] References Cited 3 Claims, 2 Drawing Figures UNITEDSTATES PATENTS 2,591,488 4/1952 Yost ..4l5/199X 7 7 4.9 1'1 1 1 1 7 7 5gl II? A a r n I [I] i r v I 1 r f l ""r-24 111 7 7 59 wry/29 w 1*" 2w I1 I 9 76 /113 /1d/ (5 27 3 PNEUMATIC MOTOR FOR MEDICAL INSTRUMENTSBACKGROUND OF THE INVENTION The invention relates to a hand-actuatedpneumatic motor for a drilling and/or milling instrument for medicalapplication. It relates especially to a small turbine used for driving aprecision drilling or precision milling instrument. The speed of suchprecision drill or precision milling instrument is very high. It ispossible, for instance, with such motor driven precision drillinginstruments or precision milling instruments to impart to the instrumentshaft a speed of about 100,000 rpm without a speed transmission gearbeing arranged between the turbine and the shaft. With knownturbine-driven precision drilling or milling instruments the airdischarged from the turbine leaves the cylindrical housing on the sideof the rotating instrument which, in the case of operations with openwounds increases the danger of infection. Another danger existingadditionally is that of an air emboly. The use of nitrogen instead ofair as a driving fluid does not completely eliminate this danger andsuffers from additional shortcomings.

Also, precision drilling instruments and precision milling instrumentshave become known which are not driven by means of a compressed airdriven turbine but by means of a compressed air driven piston sicklemotor, the pistons of which consist of individual discs rotatingeccentrically with respect to the axis of rotation. With such pistonmotor driven precision drilling instruments or precision millinginstruments it is possible to supply and to discharge the air at thedrive end of the housing, i.e. to the end facing away from the tool.Such compressed-air motors, however, in case of high speeds tend toproduce disturbing noises. In addition, with such motors the fineness ofthe work is not guaranteed under all conditions. Finally, suchcompressed air motors develop a higher torque than compressed-airturbines which might induce the doctor to demand a higher torque byexerting a pressure on the drill or the milling instrument which mightimpair the precision of the work.

SUMMARY OF THE INVENTION It is the object of the invention to provide aturbine driven rotating instrument for medical application in which thegas leaving the turbine is discharged away from the area of theinstrument.

The hand operated pneumatic motor for a drilling or milling instrumentcomprises a cylindrical housing, a shaft supported in the housing andprojecting from one front side thereof and a compressed gas driventurbine adapted to drive the shaft.

In accordance with the invention the compressed gas is supplied anddischarged at the end (input end) of the housing facing away from theshaft projecting end (output end) with the fluid gas inlet end of theturbine facing toward the output end of the housing and the fluid gasexit end of the turbine facing toward the input end of the housing, andthe compressed gas is supplied to the inlet end of the turbine throughchannels arranged along the outer periphery ofthe turbine.

Thus, the flow direction of the compressed air is reversed within thehousing. The compressed air flows from the input end of the housingtoward the output end thereof until it approximately arrives at theinlet nozzles of the turbine. Within the turbine the air flows in theopposite direction to the exit end of the turbine which is arrangedtowards the input end of the housing.

Small amounts of air might still escape at the inlet end of the turbinetowards the tool because the air at the exit from the nozzles, i.e.directly before entering the blades of the turbine rotor, is subjectedto an impact pressure, i.e. a certain overpressure which might drivesmall amounts of air through the output end towards the instrument. Hereit must be taken into consideration that a certain running clearancemust necessarily be provided between the exit end of the nozzles and theinlet end of the blades of the turbine rotor.

To avoid also the exit of these small amounts of air, the nozzle memberwith the nozzles is provided with a bushing extending towards theturbine exit end, said bushing having a small running clearances withboth the instrument shaft and the turbine rotor. These small runningclearances constitute additional flow resistance which prevent thesesmall amounts of air from escaping at the output end of the housingtowards the instrument. The suction effect of the gaseous jet leavingthe nozzles is so great that even a vacuum is formed which draws in acertain amount of air from the output end of the housing and drives itthrough the turbine to the turbine exit end.

The invention in addition offers the advantage that it is possiblewithout any difficulties to dimension the channels for the gas leavingthe turbine so amply that practically the entire gas pressure availablemay be transformed into a high velocity and thus into turbine energy.

In a preferred embodiment of the invention, the turbine is constructedto have two stages with a stator arranged between the two stages.

Suitably, the two stages of the turbine are arranged on a turbine rotorcommon to both stages, said stator being constructed in two stages inthe form of two annular halves. After having pushed the two annularhalves of the stator into a corresponding annular groove of the turbinerotor, the stator is fixed on its outer periphery inside the housing bymeans of correspondingly designed bushings. This is a very simple mannerof fixing the stator, however, other constructions are not excluded.

It is recommendable to supply the pressure gas at the input end of thehousing through a centrically arranged line and to lead off the exhaustgas at the input end via a likewise approximately centrically disposedconduit of larger diameter which surrounds the pressure gas line.

Suitably, a manually operated control valve or a manually actuatedcontrol slideis arranged in the housing near the inputend thereof.

An element to actuate the control valve or control slide is adapted toact on a brake member, which with a closed control valve or the controlslide brakes the instrument shaft.

Suitably, the brake member is held in its brake release position bymeans of a spring and is movable into its braking position in dependenceon the closing of the control valve or the control slide. A positiveactuation and braking of the tool is obtained in this mannerindependently of the respective extent of wear on the brake surface.

The brake member is suitably constructed as a centrally arranged boltwith a pivotal lever arranged between the bolt and a spring-biased slideby means of which the control valve or control slide, respectively, ismovable.

With a brake air pressure of -6 kp/cm and a direct drive of the toolshaft by means of the turbine rotor the invention secures a speed ofabout 100,000 rpm. The construction according to the invention isdistinguished by its low noise at that speed and in that it allows thefinest precision work with safety. Air consumption in this operation is200 to 300 l/min.

BRIEF DESCRIPTION OF THE DRAWING Further improvements and features ofthe invention are described by way of the enclosed drawing which showsone embodiment of the invention on an enlarged scale. In practice, thediameter of the cylindrical housin g only is about 20 mm.

In the drawings,

FIG. 1 shows a longitudinal sectional view of a pneumatic motorconstructed in accordance with the invention, and

FIG. 2 a partial sectional view taken on line IIII of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The cylindrical housing 1comprises an output member 2 and an input member 3, with a sleeve 4being fastened on the output member 2 by shrinking or pressing, forexample. The input member 3 is provided with an external thread 5 whichmay be threaded into a corresponding internal thread 6 of the sleeve 4.

The instrument shaft 7 is supported in the ball bearings 8, 9 and 10.

The turbine rotor consists of the rotor member 11 with the two bladerings 12 and 13. A stator 14 is stationarily arranged between the bladerings. On the lefthand side of the blade ring 12 as shown in FIG. 1, anozzle member 15 is stationarily arranged in which blowing nozzles 16are provided. Compressed air flows to the blowing nozzles 16 via anannular chamber 17 and channels 18 provided in the output member 2. Anintermediate member is provided between the sleeveshaped end 19 of theoutput member 2 and the lefthand end of the input member 3. Theintermediate member 20 is provided with a projecting sleeve 21. Theouter periphery of the stator 14 is fixedly clamped between sleeve 21and a shoulder 22 formed on the output member 2. The clamping action iseffected by pressing the input member 3 against the intermediate member20 with the aid of screw connection 5, 6.

Compressed air enters the input member 3 via the centric bore 23. It issupplied through a hose (not shown) which is screwed to the bore 24 ofthe input member 3. The compressed air flows through the radial bore 27via a control slide 25 which will be described herebelow in more detail,through an axial bore 26 and an oblique bore 28 of the input member 3 toan annular chamber 29, which is provided between the sleeve 4 on the oneside and the left-hand end of the input member 3 and the right-hand endof the intermediate member 20 on the other side. The sleeve shaped end19 of the output member 2 is provided with radial projections 30 bymeans of which this end is centrally guided within the sleeve 4. Widechannels remain open between these projections 30 for the passage of thecompressed-air from the annular chamber 29 to an annular chamber 31which is provided between the remaining part of the sleeve 19 and theoutput member 2 on the one side and the sleeve 4 on the other side.

The compressed air flows from this annular chamber 31 into the annularchamber 17 via channels 18. Then it passes via the blowing nozzles 16into the first blade ring 12. It is deviated in the stator 14 afterhaving left the first blade ring 12. Then the air flows through thesecond blade ring 13 of the turbine rotor. From here it flows throughthe chamber 32 to a plurality of exit bores 33 which are provided in theintermediate member 20 (see FIG. 2). The exit bores 33 open into bores34 of the input member 3 which terminate in a chamber 35. This chamber35 is connected with a hose or pipe 36 arranged centrally with respectto the bore 24 and through which the exhaust air is discharged into theatmosphere, for example.

In the shown embodiment, there are altogether six of the bores 33 and 34arranged in such a way to leave sufficient space between them for thebores 26, 28 through which compressed air is supplied. A runningclearance 37 is provided between the right-hand end of the nozzle member15 and the left-hand end of the turbine rotor 11. The nozzle member 15is provided with a bushing 38 extending a considerable length towardsthe input member 3. The bushing 38 is formed integrally with the nozzlemember 15. The running clearance 37 passes over into a small runningclearance 39 provided between the bushing 38 and a bore 40 of theturbine rotor 11. On the other side there is a small running clearance41 between the bushing 38 and the instrument shaft 7. The gap 37 thuscommunicates with the bearing 9 and thus with the free atmosphere at theinstrument end only through the long narrow gaps 39 and 41. It has beenfound that this construction suffices to prevent the exit of very smallquantities of air towards the instrument end.

The shaft 7 is provided with a bore 42 to receive the instrument. Theinstrument is clamped in the bore 42 by three centrally arranged wedges43, for example. These wedges are retained by a resilient sleeve 44consisting of rubber, for example, which is rigidly connected with ametallic outer sleeve 45 by vulcanization. When the instrument spindleis being plugged into the bore 42 the wedges 43 are slightly pressedoutwardly stressing the elasticity of the sleeve 44, thereby clampingthe instrument spindle.

A circular plate-shaped control slide 25 is supported in a correspondingrecess 46 of the input member 3, said control slide being provided witha sickle-shaped control opening 47. In the position shown in FIG. 1 thecontrol opening 47 connects the bore 23 through which compressed air issupplied, with the radial bore 27. The control slide is sealed bysealings 48 and is supported in its position by a disc 49. A pin 50fixedly connected with the slide 25 serves to actuate said slide, saidpin 50 being pivotally supported in an actuating slide 51. The actuatingslide 51 is forced by means of a spring 52 into a position in which thecontrol slide 25 is closed. Towards the outside, the actuating slide 51is closed by means of a sleeve 53 which surrounds the input member 3. Aslot 54 is provided in the sleeve 53 with a projection 55 of theactuating slide 51 engaging therethrough. The slot 54 constitutes anelongated hole which serves to guide the projection 55 of the actuatingslide. On the projection 55, there is mounted by means of a screw 56 anactuating rod 57 with a grip projection 58 by means of which the controlslide 25 may be operated. The actuating rod 57 is in addition guided bymeans of an elongated slot 59 provided therein and being in engagementwith a pin 60, said pin being fastened on the input member 3.

A nut 61 lies close to the inner race of the ball bearing which racerotates with the shaft 7, said nut being screwed onto a threaded end 62of the shaft 7. A brake member 63 formed as a concentric bolt is adaptedto lie close to said threaded end and is provided with a head 64. Thebrake member is axially movably guided in a bushing 65 and has its head64 pressed against a swivel beam 67 by means of a spring 66 which swivelbeam 67 is pivotally supported in a bore 68 of the input member 3. Theswivel beam 67 outer end is located in a recess in the actuating slide51 and passes through a slot 71 of a cover plate 69 which separates thecontrol slide 25 from the actuating slide 51. The slot 71 serves toguide both the swivel beam 67 and the pin 50 of the control slide 25.

In the left-hand end position (not shown) the actuating slide 51 forcesthe outer end of the swivel beam 67 to the left. In this way the brakemember 63 is also forced to the left on the front side of the threadedend 62 of the shaft 7 against the tension of the spring 66. Accordingly,with the control slide 25 closed, the shaft 7 is braked by means of thebrake member 63. The bore 26 is closed by means of a plug 72 near itsleft hand end (FIG. 1). Plug 72 separates the bore 26 sup plying thecompressed air from an annular chamber 70 on the left-hand side of theinput member 3 into which the exhaust air bores 33 of the intermediatemember open.

What we claim is:

l. A pneumatic turbine powered surgical motor apparatus for rotating amedical instrument comprising, in combination, an elongated housinghaving a longitudinal axis, an input end and an output end, a shaftrotatably mounted in said housing concentric with said axis andprojecting from said output end adapted to drive a cutting instrument, apressurized gas connection and an exhaust gas connection defined on saidhousing at said input end, an axial flow turbine having a rotorrotatably mounted in said housing concentric thereto and drivinglyconnected to said shaft, said turbine having an inlet disposed towardsaid housing output end and an exit disposed toward said housing inputend, first passage means longitudinally defined in said housingconcentrically extending about the periphery of said turbine andcommunicating with said pressurized gas connection and said turbineinlet, and second passage means defined in said housing communicatingwith said exhaust gas connection and said turbine exit wherebypressurized gas entering said pressurized gas connection and firstpassage flows toward said housing output end to said turbine inlet,enters said turbine inlet and reverses its direction of flow to flowthrough said turbine toward said housing input endand from said turbineexit to said exhaust gas connection.

2. In a pneumatic turbine powered surgical motor apparatus as in claim1, a nozzle member within said housing located adjacent said turbineinlet, nozzles defined in said nozzle member for directing pressurizedgas into said turbine, said nozzle member including an annular bushingcircumscribing said shaft and extending toward said turbine exit andbeing radially spaced from said shaft and turbine rotor by small runningclearances.

3. In a pneumatic turbine powered surgical motor apparatus as in claim 1wherein said first passage means comprises an annular chamberconcentrically disposed about said turbine and said second passage meanscomprises a plurality of passages axially defined in said housingextending between said turbine exit and said exhaust gas connection.

Disclaimer 3,709,630.F'r2'tz G. Pohl and Amwlcl Keller,Kiel-Dietrichsdorf, Germany. PNEUMATIC MOTOR FOR MEDICAL INSTRUMENTS.Patent dated Jan. 9, 1973. Disclaimer filed Feb. 25, 1974, by theassignee, H owmet International, Inc. Hereby enters this disclaimer toclaims 1 and 3 of said patent.

[Ofilcial Gazette March 26, 1974.]

1. A pneumatic turbine powered surgical motor apparatus for rotating amedical instrument comprising, in combination, an elongated housinghaving a longitudinal axis, an input end and an output end, a shaftrotatably mounted in said housing concentric with said axis andprojecting from said output end adapted to drive a cutting instrument, apressurized gas connection and an exhaust gas connection defined on saidhousing at said input end, an axial flow turbine having a rotorrotatably mounted in said housing concentric thereto and drivinglyconnected to said shaft, said turbine having an inlet disposed towardsaid housing output end and an exit disposed toward said housing inputend, first passage means longitudinally defined in said housingconcentrically extending about the periphery of said turbine andcommunicating with said pressurized gas connection and said turbineinlet, and second passage means defined in said housing communicatingwith said exhaust gas connection and said turbine exit wherebypressurized gas entering said pressurized gas connection and firstpassage flows toward said housing output end to said turbine inlet,enters said turbine inlet and reverses its direction of flow to flowthrough said turbine toward said housing input end and from said turbineexit to said exhaust gas connection.
 2. In a pneumatic turbine poweredsurgical motor apparatus as in claim 1, a nozzle member within saidhousing located adjacent said turbine inlet, nozzles defined in saidnozzle member for directing pressurized gas into said turbine, saidnozzle member including an annular bushing circumscribing said shaft andextending toward said turbine exit and being radially spaced from saidshaft and turbine rotor by small running clearances.
 3. In a pneumaticturbine powered surgical motor apparatus as in claim 1 wherein saidfirst passage means comprises an annular chamber concentrically disposedabout said turbine and said second passage means comprises a pluralityof passages axially defined in said housing extending between saidturbine exit and said exhaust gas connection.